Use a prepared query for historyContains.

This is called often, hopefully a prepared query will speed it up.
This also modifies Query.run to return self for easier chaining, so you
can use `query.run.value()` instead of `query.run` ; query.value()`.

qutebrowser/browser/history.py

@@ -79,6 +79,7 @@ class WebHistory(sql.SqlTable):
         super().__init__("History", ['url', 'title', 'atime', 'redirect'],
                          parent=parent)
         self.create_index('HistoryIndex', 'url', where='not redirect')
+        self._contains_query = self.contains_query('url')
         self._between_query = sql.Query('SELECT * FROM History '
                                         'where not redirect '
                                         'and not url like "qute://%" '
@@ -97,7 +98,7 @@ class WebHistory(sql.SqlTable):
         return utils.get_repr(self, length=len(self))
 
     def __contains__(self, url):
-        return self.contains('url', url)
+        return self._contains_query.run([url]).value()
 
     def _add_entry(self, entry):
         """Add an entry to the in-memory database."""

qutebrowser/misc/sql.py

@@ -83,6 +83,7 @@ class Query(QSqlQuery):
         if not self.exec_():
             raise SqlException('Failed to exec query "{}": "{}"'.format(
                                self.lastQuery(), self.lastError().text()))
+        return self
 
     def value(self):
         """Return the result of a single-value query (e.g. an EXISTS)."""
@@ -140,17 +141,14 @@ class SqlTable(QObject):
         q.run()
         return iter(q)
 
-    def contains(self, field, value):
-        """Return whether the table contains the matching item.
+    def contains_query(self, field):
+        """Return a prepared query that checks for the existence of an item.
 
         Args:
             field: Field to match.
-            value: Value to check for the given field.
         """
-        q = Query("Select EXISTS(SELECT * FROM {} where {} = ?)"
-                  .format(self._name, field))
-        q.run([value])
-        return q.value()
+        return Query("Select EXISTS(SELECT * FROM {} where {} = ?)"
+                     .format(self._name, field))
 
     def __len__(self):
         """Return the count of rows in the table."""

tests/unit/misc/test_sql.py

@@ -94,15 +94,20 @@ def test_contains():
     table.insert(['one', 1, False])
     table.insert(['nine', 9, False])
     table.insert(['thirteen', 13, True])
-    assert table.contains('name', 'one')
-    assert table.contains('name', 'thirteen')
-    assert table.contains('val', 9)
-    assert table.contains('lucky', False)
-    assert table.contains('lucky', True)
-    assert not table.contains('name', 'oone')
-    assert not table.contains('name', 1)
-    assert not table.contains('name', '*')
-    assert not table.contains('val', 10)
+
+    name_query = table.contains_query('name')
+    val_query = table.contains_query('val')
+    lucky_query = table.contains_query('lucky')
+
+    assert name_query.run(['one']).value()
+    assert name_query.run(['thirteen']).value()
+    assert val_query.run([9]).value()
+    assert lucky_query.run([False]).value()
+    assert lucky_query.run([True]).value()
+    assert not name_query.run(['oone']).value()
+    assert not name_query.run([1]).value()
+    assert not name_query.run(['*']).value()
+    assert not val_query.run([10]).value()
 
 
 def test_delete_all(qtbot):